<template>
  <div>
      <h4>第七题</h4>
    <p>请选择你要购买的书籍</p>
    <ul>
        <li v-for="(obj,index) in arr" :key="index">
            <span>{{ obj.name }}</span>
            <button @click="buy(index)">买书</button>
        </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(obj,index) in arr" :key="index">
          <td>{{ index + 1 }}</td>
          <td>{{ obj.name }}</td>
          <td>{{ obj.price }}</td>
          <td>{{ obj.count }}</td>
          <td>{{ obj.count * obj.price }}</td>
      </tr>
    </table>
    <p>总价格为: {{ sum }}</p>
  </div>
</template>

<script>
export default {
  data () {
    return {
      arr: [
        {
          name: '水浒传',
          price: 107,
          count: 0
        },
        {
          name: '西游记',
          price: 192,
          count: 0
        },
        {
          name: '三国演义',
          price: 219,
          count: 0
        },
        {
          name: '红楼梦',
          price: 178,
          count: 0
        }
      ]
    }
  },
  methods: {
    buy (i) {
      this.arr[i].count++
    }
  },
  computed: {
    sum () {
      return this.arr.reduce((accu, obj) => accu + obj.count * obj.price, 0)
    }
  }
}
</script>
